1. Field of the Invention
The present invention relates to a light sand-gravel for general construction usage and its production methodology. More particularly, the present invention is directed to a light sand-gravel of various specific gravities, depending on its end use, namely, that with a specific gravity of 1.5.about.1.8 is for a heavy construction purpose, a specific gravity of 1.2.about.1.5 is for a general building purpose, and a specific gravity of 0.4.about.1.2 is for a light partition. With a specific gravity greater than 1.8, such is for a special purpose. The production methodology involves a sand-gravel that when properly treated and applied as the aggregate for light concrete, that concrete has greater strength but a small er specific gravity compared to that of the prior art.
2. Prior Art
Rock materials when used for a construction purpose generally are in the forms of flagstones and granules. The former is used as a finishing material and usually as an external surface for flooring installations, while the latter, depending on its grain size and specific gravity (strength), is usually used as a grading or concrete aggregate. The source of the granules is mostly gravel from riverbeds, and the specific gravity of such granules is always greater than 2.6. The inherited weight of such granules when used in the site foundation or the structure of a building with a low number of floors is directly borne by the earth bed, and has negligible, if not minimal, impact upon the overall structure or cost. However, the very limited availability of land has forced buildings to be constructed as high-rise buildings. Weight and cost of materials for such buildings have developed into the bottleneck in the structural design thereof.
So far, weight of construction material has been a very critical element in the design of buildings. Therefore, a wall panel to be used for the external curtain wall or a partition usually requires a light-weight and sufficient strength of the composite construction, in most cases. Such a design is found with the disadvantages of a complicated preparation, higher cost and significant waste material due to mass pre-casting of units followed by a cutting operation, resulting in problems in subsequent processes.
A wall panel comprised of light-weight foam cement is another type of curtain wall. In strict terms of weight, foam cement board is lighter than the general RC wall, but the wall panel erected with foam cement board is vulnerable to impact. A nail, hook or an object hanging upon the foam cement board will cause the nail or hook to be pulled off.
There is an absence of a better substitute for the partition materials on the market. The strength of the material, depending on the requirements, governs the selection of material, though such material may be very expensive and heavy, or lighter and cheaper, but at the expense of strength. Those light partition materials available on the market are far from an efficient alternative for a structural aggregate, either for the consideration of strength or cost.
Although in the field of the emergence industrial ceramics, ceramics may be used as a structural or construction material, its specific gravity remains at the higher end of the spectrum (above 3). Factors such as the highly demanded purity of some of the ceramic material and demanding quality contribute to an even higher cost for those materials. In addition, the production of ceramic material is very limited. Ceramic materials may give the advantage of excellent strength, industrial ceramics can only be applicable to certain special products. So far, industrial ceramics are used only for traditional tile, ground tile, and light cement, but never as an aggregate.
Furthermore, rock materials have been comprehensively applied in foundation grading in the construction industry. However, should such foundations form a cluster on alluvial land, the buildings thereon will cause a gradual land subsidence. Indeed, use of a grading material with a heavier specific gravity is one of the main factors for such land subsidence.
This invention solves the problems observed in the prior art, by seeking from the natural world for an alternative to substitute for the existing building materials containing crushed rock. The substitute must be "hard yet light", cheaper and allow easy access. However, all existing mineral stones fail such efforts since they are hard and solid. The only hard artificial building material known up to now is that of ceramics, but its specific gravity is greater than 3 and the production cost is high. Most of the "light gravels" available on the market are light but with insufficient strength. Granules made from natural mineral stones are limited in supply and very expensive, which prevents them from being used on an economic scale, and they are available in a narrow range of specific gravity. Thus, they are very limited in their application. As for those grains made from slag or other metallurgic residuals, such at best have the property of a smaller specific gravity. When granulated with traditional cement or other cementitious materials, or stirred to become granulated, and then heated to harden, such granules remain with a greater specific gravity (i.e. very limited changes in its volume), poor strength, limited supply and application, and higher production cost.
The formation of a structure of light granules is very difficult to produce in the natural world (or more appropriately, such formation has not yet been discovered so far). Whereas, natural resources of mineral stones are constantly under high temperature and pressure, the same conditions that exist when they are released (e.g. an eruption from volcano). Once released, they are subject to a sudden decrease in temperature. Therefore, hard rocks with a vitreous surface, though they may be found with certain natural mineral stones, are formed either from lava or volcanic dust and have the characteristics of being hard and solid, great specific gravity, and brittle, making them not a good light granule for construction applications.